Example embodiments of inventive concepts relate to an analog-to-digital converter (ADC), such as an ADC for amplifying an input, an image sensor including the same, and/or an image processing device including the image sensor.
An image sensor is a device that converts an optical image signal into an electrical image signal. Sensitivity control is a basic function of the image sensor. Sensitivity is controlled by adjusting the gain of a result of correlated double sampling (CDS) before to perform analog-to-digital conversion of the CDS result. For this operation, the image sensor includes a programmable gain amplifier (PGA) circuit between a CDS circuit and an ADC.
Since the PGA circuit is implemented using a plurality of capacitors, mismatch occurs between the capacitors. Moreover, since an ADC is connected to each of columns in a two-dimensional pixel array of the image sensor, the PGA circuit is provided for each column, which increases an entire area of the image sensor.